This invention relates generally to gas sensors, and more particularly to a gas sensor for use, for example, in a fuel cell system.
In general, a polymer electrolyte fuel cell is provided in the form of a fuel cell stack comprised of a plurality of stacked cells each having an anode, a cathode, and a solid polymer electrolyte membrane sandwiched between the anode and the cathode. The anode is supplied with hydrogen as a fuel, and the cathode is supplied with air as an oxidant, so that hydrogen ions produced by catalytic reaction at the anode migrate through the solid polymer electrolyte membrane to the cathode in which the hydrogen ions and the oxygen react electrochemically to generate electricity.
In such a polymer electrolyte fuel cell or other type of fuel cell, generally, unreacted air discharged from the cathode (which is called “exhaust gas”) is forced to the outside of the system, and the exhaust gas should be checked, before released to the outside, to ensure that no hydrogen gas is contained therein. Thus, a hydrogen sensor to detect a hydrogen gas is used to monitor the exhaust gas.
Among gas sensors used for such a hydrogen sensor is a gas sensor, as proposed in US 2005/0042141 A1, in which a gas-sensing element is provided in a gas-sensing chamber and a circuit board provided on the outside of the gas-sensing chamber is connected to the gas-sensing element.
If the gas sensor as disclosed in US 2005/0042141 A1 were provided in a relatively high-temperature or relatively high-humidity environment, the heat-resisting and moisture-proof properties of an integrated circuit or microcomputer mounted on the circuit board for control would become matters of grave concern.
There is a need of a gas sensor suitable for use in a high-temperature or high-humidity environment, such as in a fuel cell system. The present invention has been made in an attempt to address the above problems and needs.
Illustrative, non-limiting embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an illustrative, non-limiting embodiment of the present invention may not overcome any of the problems described above.